1. Field of the Invention
The present invention relates to a robot cleaner, and particularly, to a moving distance sensing apparatus for a robot cleaner and a method therefor capable of sensing precisely a moving distance of the robot cleaner by mounting a short distance sensor and a long distance sensor on the same sensing line.
2. Description of the Related Art
In general, a robot cleaner is a machine for automatically cleaning where to clean by sucking foreign materials such as dust from a floor while travelling around there by itself without a handling by a user.
FIG. 1 is a block diagram showing a configuration with respect to a travelling system of a conventional robot cleaner.
As can be seen from FIG. 1, a travelling system of the conventional robot cleaner is comprised of: an obstacle sensing unit 1 for sensing an obstacle during a movement of the robot cleaner; a motor controlling unit 2 for outputting a motor control command signal to keep away from the obstacle depending on an obstacle sensing signal outputted from the obstacle sensing unit 1; a left-side-wheel motor driving unit 3 for driving a left-side-wheel motor 5 in response to a motor control command signal inputted from the motor controlling unit 2; and a right-side-wheel motor driving unit 4 for driving a right-side wheel motor 6 in response to the motor control command signal inputted from the motor controlling unit 2.
FIG. 2 is a flow chart showing an operation with respect to a moving method for the conventional robot cleaner.
Referring to FIG. 2, once a user instructs a robot cleaner to clean, the robot cleaner carries out a cleaning operation and recognizes whether there is an obstacle to be sensed (steps ST1˜ST3). At this time, if an obstacle is sensed, the robot cleaner performs an operation to keep away from the obstacle by driving the left-side or right-side wheel motor (step ST4). After avoiding the obstacle, the robot cleaner keeps going straight and then performs the cleaning operation again until it is completed (steps ST5 and ST6). Finally, when the cleaning has been done, the robot cleaner stops its movement (step ST6).
As aforementioned, the robot cleaner performs a cleaning operation with travelling a predetermined path or an arbitrary path or avoiding obstacle by means of a program installed therein. However, in order to carry out the cleaning operation, various information such as a location determination, measurement of a travelling range, sensing obstacle, or the like, should be provided for the robot cleaner, for which many sensors are required. In particular, the robot cleaner should have a sensing system which can sense a long distance and a short distance at the same time and also sense a mis-operation. However, a sensor like a laser sensor capable of precisely sensing the long and short distances requires a high price so that it is difficult to apply it to the robot cleaner. Additionally, in case of using a low price of sensor such as a ultrasonic sensor, once sensing a long distance to a specific object while the robot cleaner moves, thereafter, when measuring a short distance with respect to the same object, error can be disadvantageously occurred during measuring the distance due to a slip or a sensor error, thereby frequently occurring a mis-operation of the robot cleaner.